Hi. I've got a Zongshen 250, watercooled 4 speed + reverse. I have just got it going and it is running rough. Is there a way to change the timing ??? It's got a CDI ignition and the stato bolts to the inside of the engine cover with the flywheel hub direct off the crank. by taking the flywheel off and turning it slightly, can this work or are these flywheel's key-way'd with static timing ?? I have just removed the side-cover but am now waiting on a flywheel remover, so I can't see that part yet. Any help would be greatly appreciated.

J.

 

The flywheel is keyed to the crankshaft and isn't adjustable. So the timing is specified by the key on the crankshaft versus the mechanical position of the timing pickup coil on the stator, versus the raised bump on the flywheel. All of these are fixed and not adjustable.

But it is not true that the ignition timing is "static". The trigger signal amplitude generated by the pickup coil is directly proportional to engine speed. The CDI triggers at a fixed voltage on the rising leading edge skirt of this waveform (and not at the peak voltage which always occurs at the same place in an engine rotation). When the trigger voltage rises with engine speed the leading edge of this waveform rises a bit too, and the trigger threshold in the CDI is then reached a little earlier. Thus there is some timing advance built into the ignition system based on engine speed.

I suspect you problem is carburetion - not ignition timing.

 

Ok. Thanks for that info. Everything is brand new, and almost everything has needed re-building out of the box even though it was apparently 'tested and tuned'.
The reason I was thinking timing is because it is extreemly hard to start and back-fires, a lot, as if the spark is to far advanced.
I'll rip the carby down tonight and check it.

Thank you.

 

The timing seems retarded, sorry. or maybe inlet valve is set wrong.

 

Check the ignition timing with a timing light. Usually quads have an access screw plug that allows shing a timing light onto the flywheel to see the timing marks.

I still doubt this is your problem.

Tight valves make a quad really hard to start, but once warmed up the quad runs and starts great. Only when the quad cools *all* the way back down does it get hard to start again. Loose valves start up fine but make valve clatter noise.